Please help: Speaker wire ?

It may not be your cables. Unless components are properly isolated from internal/external vibration, they won't provide a rich harmonic structure. If that is covered (it seldom is) then look at your speaker cables, but in a different way. They act as antenna for RFI/EMF, and other junk noise that comes out of the speakers a bright sound. Walker Audio makes a great product for this. To learn more about tweaking, check out www.audiotweakers.com

Check out www.interlinkhouse.com for Stealth speaker cables, and contact their designer for a particular recommendation. No risk since there's a 30-day money-back guarantee. I've used two more expensive than you want, Premier and Ultimate Ribbon, and found both to be outstanding. Lower down in price you can at least expect them to be very competitive with other brands.

For our budget of $350, get a pair of MIT Terminator2 bi-wire. It's will warm the sound and will not lose any detail.

I second it, MIT Terminator 2 Bi-wire! I'm about to get some single wire ones from Audio Advisor. These are close-out priced, so it'd be foolhardy to miss out. My Terminator 3 ones are beating everything I've thrown at them, including Cardas Neutral Reference, AudioTruth Dragon, Kimber 8TC, Straightwire Virtuoso, and anything Goertz. I'm also about to try Analysis Plus Oval 9, but I don't expect much from it. The reviews I've read on that one seem biased and based on ignorance. BTW, none of MIT's networks contains an "equalizer", and they have zero components of any kind in the signal's path...unlike all of Transparent's cable.

I think changing the wire to cure brightness is a strange approach. Have you considered hanging a rug, tapestry or foam in the room in strategic places to help take the edge off? I highly doubt the wire is the culprit unless you are using very thin cheap junk. Probably the room is what needs tuning. Good Luck!